For approximately one and a half decade, under-spring arrangements for beds have been on the market by means of which an anatomically improved reposing surface has been attained relative to the old conventional coil spring frames. Such arrangements include resilient wooden laths disposed transverse to the longitudinal body axis and retained at their two ends in support members which consist of an elastic material and are therefore able to move flexibly, i.e. to follow the body contour. These beds constitute an advance compared with all earlier systems and even in relation to those which have a rigid lateral bearing. Preponderantly, upper mattresses of foamed material are used as upper covers for such lath-type under-spring arrangements.
Owing to their inherent spring properties, as well as their ability to retain heat, these upper mattresses are very suitable. However, endeavors must be made to render the pressure support area as large as possible. The lath-spring arrangement causes some difficulties. A spring lath requires a certain thickness in order to maintain its stability but it must exhibit a certain carrying power which can then be regulated only by varying the width of the spring lath in the systems known heretofore.
Conventional bed-like articles of furniture commercially obtainable at present are furthermore known to form a functional unit of different co-operating systems. These known structures admittedly afford character to the bed-like article of furniture as a whole, but must be constructed and built in individually and also become effective separately when in use. Accordingly, there are differentiated in the usual bed-like articles of furniture inter alia
(1) the support system which effects the resilient mounting of the transverse laths, PA0 (2) the possibility of regulating the hardness (spring characteristic) of the transverse laths (e.g. in the case of overweight), and PA0 (3) devices for adjusting the height of individual groups of transverse laths (lumbar or shoulder portions), wherein heretofore the step-less height regulation of individual transverse laths (for orthopaedic use at any desirable location) of the bed-like article of furniture was not realizable.
Every single one of these three systems was developed further from relatively primitive beginning in the course of the last two decades, with constant improvement of the lying and sleeping comfort. However, there has been no success in combining the three-fold operational effect in a single system.
Considered from the two-fold point of view of load absorption and ventilation, the spring lath arrangement of a bed-like article of furniture must be adjusted to two mutually contradictory criteria. For a given lath thickness, the spring lath must be as wide as possible in view of the absorption of large forces and the avoidance of excessive bending-through. However, the lying surface is well ventilated when narrow laths are selected which have large gaps providing access for air.
Since the specific pressure absorption and bending ability of a spring lath is substantially determined by the thickness thereof and the latter constitutes a given quantity in the selection of the spring lath parameters, the constructor of the bed-like article of furniture still has the selection of the width and the mutual spacings of the spring laths. Here, however, the two-fold criterium referred to above sets a clear limit. Thus, in most cases, the bed-like articles of furniture known heretofore were either badly ventilated or possessed insufficient support properties.